1. Field of the Invention
The present invention relates to a method of manufacturing a substrate for liquid crystal display device and a method of manufacturing a liquid crystal display device using same. More particularly, the present invention relates to a method of manufacturing a substrate for MVA type or transreflective liquid crystal display device and a method of manufacturing a liquid crystal display device using same.
2. Description of Related Art
As a liquid crystal display device having a high viewing angle there is used an MVA (Multi-domain Vertical Alignment) type liquid crystal display device. An MVA type liquid crystal display device comprises a vertically-aligned liquid crystal sealed interposed between a thin film transistor (TFT) substrate and an opposite substrate and an alignment controlling structure formed on at least one of the two substrates for controlling and dividing the alignment of the liquid crystal into a plurality of alignment regions within the pixel region. As such an alignment controlling structure there is used an alignment controlling protrusion formed by a dielectric material or the like. By controlling the alignment of the liquid crystal, an MVA type liquid crystal display device can be provided with a drastically enhanced viewing angle.
However, the conventional MVA type liquid crystal display device is disadvantageous in that it has different γ characteristics between in the direction perpendicular to the surface of the display (front direction) and in the direction oblique to the surface of the display. As a method for overcoming this difficulty there has been proposed a method which comprises providing a plurality of regions having different threshold voltages in a pixel to relax the change of γ characteristics in the oblique direction. In order to provide regions having different threshold voltages in a pixel, a dielectric layer capable of lowering the effective voltage applied to the liquid crystal layer is provided in a part of the pixel.
FIG. 25 illustrates the sectional configuration of the opposite substrate in a conventional MVA type liquid crystal display device comprising a dielectric layer provided therein. As shown in FIG. 25, an opposite substrate 104 comprises a light-shielding layer (BM) 148 formed on a glass substrate 111 for defining the pixel region, color filter (CF) layer 140 formed every pixel region and a common electrode (not shown) formed on the entire surface of the substrate of the CF layer 140. A dielectric layer 146 is formed on the common electrode and on a part of the pixel region. On the dielectric layer 146 is formed an alignment controlling protrusion 144 for dividing alignment. This arrangement is advantageous in that the resulting liquid crystal display device exhibits improved display properties but is disadvantageous in that a step of forming the dielectric layer 146 is required, adding to the number of steps in the method of manufacturing the liquid crystal display device.
As a display device for mobile type terminals or note type personal computers there is used a transreflective type (including slightly-light transmitting type and slightly reflective type) liquid crystal display device capable of displaying in both transmission and reflection modes. The pixel regions in the transreflective type liquid crystal display device each has a reflective region having a reflective electrode formed on TFT substrate side thereof and a transmission region having a transparent electrode formed on TFT substrate side thereof. FIG. 26A illustrates the configuration of the pixel region (reflective region) of the opposite substrate in a conventional transreflective liquid crystal display device. FIG. 26B illustrates the sectional configuration of the opposite substrate of FIG. 26A taken on line X—X. As shown in FIGS. 26A and 26B, a CF layer 140 having an opening 141 is formed on a part of the reflective region on the glass substrate 111 on the opposite substrate side thereof. A common electrode 142 is formed on the entire surface of the substrate on the CF layer 140. In this arrangement, the liquid crystal display device is adapted to mix light transmitted by the CF layer 140 with light passing through the opening 141, making it possible to inhibit the drop of reflectance during display in reflection mode. Further, the formation of a dielectric layer 147 having the same thickness as that of the CF layer 140 makes it possible to approximate γ characteristics of the two modes, i.e., transmission mode and reflection mode by each other and hence realize a liquid crystal display device having a reduced difference in display properties between the two modes. The dielectric layer 147 is formed by a photolithographic process with a transparent resist.
However, a positioning error in the patterning of the dielectric layer 147 makes it likely that a misalignment in overlapping can occur between the dielectric layer 147 and the opening 141 of the CF layer 140. FIG. 27A illustrates the configuration of the pixel region of the opposite substrate having an alignment error in overlapping. FIG. 27B illustrates the sectional configuration of the opposite substrate of FIG. 27A taken on line Y—Y. As shown in FIGS. 27A and 27B, the misalignment in overlapping between the dielectric layer 147 and the opening 141 makes it impossible to fill the entire part of the opening 141 with the dielectric layer 147, leaving an opening 141′ behind.
FIG. 28 illustrates the sectional configuration of a liquid crystal display device comprising an opposite substrate having the opening 141′ left behind. As shown in FIG. 28, the reflective region comprising a reflective electrode 117 formed on a glass substrate 110 on TFT substrate side thereof is subject to light leak or disturbance of alignment of liquid crystal due to the difference in cell thickness caused by the presence of the opening 141′. As a result, the liquid crystal display device exhibits a deteriorated display quality in reflection mode.
[Patent Document]
JP-A-2000-187208